Lecture 5: Origin and diversity of seed plants

Question 1

Seed plant Reproductive strategy:

Answer 1

1) The microsporangia (potential pollen) and megasporangia (potential ovules) occur on different individual sporophytes
2) Ovules are borns on megasporophylls in megastrobili. Microspores develop into microstrobili.
3) microspores are released from sporophyte (2n) and meiosis occurs, gametophyte forms inside =POLLEN GRAIN
4) Megaspores stay attached to sporophyte; meiosis occurs but only 1/4 survive = OVULE
5) pollen grain travles in wind, lands on sporophyte&fertilises the ovule present IN SITU
6) SEED is produced (fertilised ovule), released either by animals/wind etc

Question 2

Strobili =

Answer 2

cone like structure

Question 3

Advantage to seed plant reproductive strategy

Answer 3

• no water is required for sperm to reach egg
• plant has control of ovule as is connected to it. Can receive water & nutrients from the parent plant meaning can survive for longer

Question 4

Tracheophytes:

Answer 4

vascular plants

Question 5

Trimerophytes evoked into

Answer 5

the ancestors of fern and seed plants of the Devonian period

Question 6

Progynosperms were:

Answer 6

non seed plants. Gave rise to seed plants in the last Devonian.

Question 7

Out of 12 orders of tracheophtye gymnosperms only 4 still present today:

Answer 7

• Ginkgoales
• Gnetales
• Cycadales
• Coniferales

Question 8

Pro gymnosperms description:

Answer 8

• NOT SEED PLANT; they originated from these
• first ‘tree’ like organisms
• Origin of first forests
• 8-15m in height
• Heterosporous plant

Question 9

Pteridosperms

Answer 9

• First seed plants, almost certainly evolved from pro gymnosperms ancestors.
• extinct group, represents the most primitive seed plants
• they compromise a broad, probably artificial, group incorporating plants with fern-like fronds associated with seeds.
• Ovules and microsporangia were borne on unmodified or only slightly modified foliage (i.e no cones).
• Some were tree-like (arborescent) with secondary thickenings, others had a more prostate, scrambling or vine-like habit.
• fronds (large, divided leaf) usually spirally arranged on the stem.

Question 10

Cordaites

Answer 10

• a large strap-like, spirally arranged plants confined to upper branches
• leaves are up to 1m long by 15cm wide and a parallel veined
• trunk up to 1m wide and compromises a primary stele
• extinct group of arborescent plants (tree-like) up to 30m tall

Question 11

Glossopterids

Answer 11

-by now land was rather forest dominated

Question 12

conifers

Answer 12

dominate planet